Modulating system for frequency multipliers



July l0, 1945. A. l.. NELsoN 2,380,365

MODULATING SYSTEM FOR FREQUENCY MULTIPLIERS Filed Sept. 4, 1941 2 SheeliS--Sheefl 1 r I 1 Z 2 (D (D E 5H: INVENTOR n R l.. NELSON Oz E- N BY ,July 10, l945- A. l.. NELSON v 2,380,366

MODULATING SYSTEM FOR FREQUENCY MULTIPLIERS Filed Sept. 4, 1941 2 Sheets-Sheet 2 GRID VOLTAGES.

TU BE-8 TUBE- 8 INDIVIDUAL OUTPUT cURRENTs. FIG-Q TUBE-9 TUBE-9 REsULTANT OUTPUT V/ CURRENT.

MODULATED OUTPUT CURRENT.

\ INVENToR R L. NELSON Patented July 10, 1945 MODULATING SYSTEM FOR FREQUENCY MULTIPLIERS Arthur L. Nelson, Fort Wayne, Ind., assgnor to Farnsworth Television and Radio Corporation, a corporation of Delaware Application September 4, 1941, Serial No. 409,471

8 Claims.

'I'his invention relates to a combined frequency multiplier and modulator and particularly to an arrangement for multiplying and simultaneously modulating high and ultra-high frequencies.

In the copending application U. S. Serial No. 314,480, filed January 18, 1940, by Arthur L. Nelson, there is described a new and improved frequency multiplier of the type embodiedin the present invention.

In conventional arrangements for deriving a modulated output signal from' an unmodulated rtor comprising signal repeating means adapted to repeat portions of a signal impressed thereon. An input circuit is provided for the multiplier and means so connecting the input circuit with the repeating means so as to effect a plurality of applications of a signal impressed on the input circuit to the repeating means, each of a predetermined different relative phase. Means are provided for varying the relative phase in accordance with a modulating signal and, finally, there is provided an'output circuit for the repeating means for combining repeated signal portions to produce a modulated signal of increased frequency.

In on preferred embodiment of the invention, the frequency multiplier modulator comprises a pair of similar multi-element vacuum tubes. An individual input circuit is provided for each of these tubes consisting preferably of a single transmission line. A phase shifting means, preferably comprising a transmission line, connects the `individual input circuits, and the main input'circuit for the multiplier device is connected thereto. 1 In such a multiplier employing a single pair of vacuum'tubes, frequency doubling or frequency quadrupling is readily obtained at the yoption of the user, without any changes in the input circuits and only a small change in 'the .output circuit arrangement and constants. Another transmission line'is ccnnected tothe transmission line constituting the phase shifting means and to its end remote from the main input circuit. This transmission line is of predetermined length and is terminated by one or more electron discharge devices representing a variable in'pcdence. The impedance of this device or devices is controlled in accordance with a modulating signal.

It will be understood that at the lower frequencies conventional resonant circuits employing lumped reactances may be substituted for the transmission lines between the grids of each tube, and the phase shifting means connecting the tube input circuits may be other than a transmission line, without departing from the scope of the invention.

For a Ibetter understanding of the invention, together with other and further objects thereof, reference is had to the following description, taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims. I

In the accompanying drawings, Fig. l shows a schematic circuit diagram of a frequency multiplier modulator in accordance with the present invention, arranged for frequency doubling. Fig. 2 is a graph representing certain operating characteristics of the multiplier modulator of Fig. l.

Referring more particularly to Fig. 1 of the drawings, there is shown a frequency' multiplier modulator comprising an input circuit having input terminals I and 2 connected to the control grids of a pair of amplifier tubes 3 and 4, respectively, the anodes of which are connected tothe open ends of a short-circuited transmission line 5. The eifective wave length of the transmission line 5 is one-quarter wave length of the radio frequency signal applied to the inputv terminals l and 2. The short-circuited end of the transmission line 5 is connected to the positive terminal of an anode voltage source, schematically indicated at B1i. The input circuit also includes a transmission line section 6, the wave length of which is not critical, having in each of its branches a condenser 1 for blocking the direct current from the voltage source indicated at 31+. For repeating portions of the radio frequency signal applied to the input terminals I and 2, there are provided a pair of vacuum tubes 8 and 9, each having two control grids and a single anode. Obviously, two separate tubes can also be used with their anodes conductively connected in place of each of the tubes 8 and 9. Tubes 8 and 9 are each provided with an input circuit comprising transmission lines I0 and ll, respectively. These transmission lines, having an eective wave length equal to one-quarter wave length of the 'applied radio frequency signal, are shortcircuited at one end, while their open ends are connected to the control grids of tubes 8 and 8, respectively. Lines I8 and II are conductively connected at points AA and BB, respectively, to the opposite ends of a transmission line I 2, whose eil'ective wave length equals one-quarter wave length of the applied radio frequency signal and which constitutes a phase-shifting means for applying the input signal to the control grids of tubes 8 and 9, with a predetermined diilerent phase relation. For providing the control grids of tubes 8 and 8, respectively, with a steady bias voltage, there is provided a voltage source indicated as a battery I3, connected to the shortcircuited end of the transmission line II at a point C. Battery I3 supplies the-bias voltage to the control grids of both tubes, since they are at the same direct-current potential.

For changing the phase of the input signal applied to the control grids of tubes 8 and 8, respectively, there is provided a transmission line section I4 connected to the transmission line I2 at points BB and having connected to its opposite end a pair of electron discharge tubes I5 and I6. For blocking the anode voltage of tubes I5 and I8 from the remainder of the circuit,

transmission line I4 is provided with condensers I1, as shown. The eiective wave length of the transmission line I4 is one-eighth -the wave length of the applied radio frequency input signal. Tubes I5 and I8 each comprise an anode, a control grid and a cathode. The cathodes of both tubes are connected to ground. For the purpose of varying the variable impedance represented by the tubes I5 and I8, there are provided between the control grids and the cathodes, respectively, of tubes I5 and I6 a pair or input terminals I8 and I8, adapted to have a modulating signal applied thereto. For by-passing radio frequency signals arriving at the control grids of tubes I5 and I8, through the anode grid capacities thereof. there are provided a pair of by-pass condensers 20 and 2I, connected between the control grids of tubes I5 and I6, respectively, and ground. For supplying the tubes I5 and I8 with operating voltages, there is provided a transmission line section 22 connected at one end to the anodes of these tubes while its opposite end is short-circuited. The short-circuited end of transmission line 22 is connected to the positive terminal of an anode voltage source schematically indicated at 132+. The effective wave length of the transmission line 22 is one-quarter of the wave length of the applied radio frequency signal.

For developing a modulated radio frequency signal of increased frequency, there is provided a common output circuit connected to the anodes of tubes 8 and 8, respectively, comprising a transmission line 23 having one end connected to the anodes of tubes 8 and 8 and having its opposite end short-circuited. The short-circuited end of transmission line 23 is connected to the positive terminal of an anode voltage source schematically indicate at Ba+ for applying an operating voltage'to the anodes of tubes 8 and 9. The effective wave length of this transmission line is equal to one-quarter of the wave length of the multiplied and modulated radio frequency signal. v

For deriving a modulated signal of increased frequency from the transmission line 23, there are provided a pair of contacts 24 and 25, slidably arranged on the transmission line 23 for the purpose of impedance matching and connected to a pair of output terminals 25 and 21,

between which a modulated signl 0f increased frequency is developed.

In operation, a radio frequency signal is applied to the input terminals'l and 2, amplified by means of amplifier tubes 3 and I and applied by way of the transmission line i to points AA of the transmission line I2. If the transmission line I2 were terminated at points BB with .the proper resistance, the input signal would be applied to the control grids of the tube 8, with a phase difference of 180. The same signal would be applied to the control grids of tube 8, also, with a phase difference of 180; however, the signals applied to corresponding grids of the two tubes would have a relative phase diiference of due to the presence of the quarter-wave length transmission line I2. The voltages applied to the control grids of tubes 8 and 8 are shown in Fig. 2. Due to the bias voltage supplied by the source I8 to the control grids. these tubes are permitted to draw current only during a portion of the applied signal, so that individual output currents, as shown in Fig. 2, are delivered by the tubes 8 and 8 to the output circuit comprising the transmission line 28. The resultant output current resulting therefrom is also shown in Fig. 2.

If, now, the resistance assumed between points BB of transmission line I2 is replaced by a variable impedance coupled to points BB by way of the one-eighth wave length transmission line Il, different operating conditions are incurred. Assuming the impedance represented by the tubes I5 and IB to be Z. and the characteristic impedance of the transmission line Il to be Za, then the impedance, looking from terminals BB to the left, is

Assuming the characteristic impedance of transmission line I2 also to be Zo, then the impedance at points AA, looking to the left will be The angle between these impedances and, therefore, the. relative phase of the voltages appearing between points AA and BB is From the above, it is evident that the relative phase of the voltages at points AA and BB and, therefore, also of the voltages applied to the control grids of tubes 8 and 8, respectively, varies in accordance with variations of the impedance Z., represented by the tubes I5 and I8. The impedance represented by these tubes, however, is varied in accordance with the modulating signal applied to theinput terminals I8 and I8. Hence, the relative phase of the individual output currents contributed by tubes 8 and 8 is varied in accordance with the modulating signal, whereby the amplitude of the resultant modulated output current is decreased, as shown in Fig. 2. In this manner, a radio frequency output signal having twice the frequency of the applied radio frequency vis produced, which is modulated in accordance with a modulating signal.

While there has been described what is at present consideredthe preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A frequency multiplier modulator for multiplying the frequency of anl input signal comprising a pair of vacuum tubes, each having two grids and one anode,l an input circuit, a transmission line having an effective length equal to one-quarter the wave length of said input signal l0 connected to said input circuit, means connecting the grids of one of said tubes to opposite sides of said transmission line at one end thereof, means connecting the grids of the other of said tubes at opposite sides ofr said transmission line at the other end thereof, a similar transmission line having an effective length equal to one-eighth the wave length of said input signal connected to said first-named transmission line at its endremote from said input circuit, an impedance means connected to said transmission line and variable in accordance with a modulating signal and a common output circuit connected to said anodes to produce a modulated signal ofincreased frequency. 25

2. A frequency multiplier modulator for multiplying the frequency of an input signal comprising a pair of vacuum tubes, each having two grids and one anode, an input circuit, a first transmission line having an effective wave length equal to one-quarter the wave length of said input signal connected to said input circuit, second and thirdjr transmission lines, respectively, for each of said tubes having an effective length equal to onequarter the wave length of said input signal connecting the grids of said tubes to opposite ends, respectively, of said rst transmission line at opposite sides thereof, a fourth transmission line connected to the end of said rst transmission line remote4 from said input circuit and having 40 an effective wave length equal to one-eighth the wave length of said input signal, impedance means terminating the open end of said fourth transmission line and being variable in accordance with a modulating signal, and a common output circuit connected to said anodes to produce a modulated signal of increased frequency.

3. A frequency multiplier modulator comprising a pair of vacuum tubes each having two grids and one anode, an individual input circuit for each of said tubes connected to the grids thereof, phase shifting means connected between relatively low impedance points of said individual input circuits,

a common input circuit connected to one end of said phase shifting means whereby a signal may be applied to the grids of the same tubein opposite polarity and to corresponding grids of different tubes with predetermined different relative phase, phase shifting means including a variable impedance means connected to said rstnamed phase shifting means for varying said relative phase, and a common output circuit connected to said anodes to produce a modulated signal of increased frequency.

4. A frequency multiplier modulator for multiplying the frequency of and modulating the amplitude of an input signal comprising a pair of vacuum tubes, each having two grids and one anode, an individual input circuit for each of said tubes connected to the grids thereof, phase shifting means connected between the relatively low impedance points of said individual input circuits, said phase shifting means comprising a transmission line having an veiective length equal to onequarter the wave length of said input signal, a

common input circuit connected to one cud of said phase shifting means whereby a signal may be applied to the grids of the saine tube in opposite polarity and to corresponding grids of the different tubes in predetermined different relative phase, a second transmission line connected'to the ends of said first-named transmission line remoto from said common input circuit, an 'impedance means connected to the terminals of said second transmission line and variable in accordance with a modulating signal, and a common output cir- 1 cuit connected to said anodes to produce a modulated signal of increased frequency.

5. A frequency doubler modulator for providing a modulated output signal having twice the frequency of an unmodulated input signal comprising a pair of vacuum tubes, each having two grids and one anode, an individual input circuit for each of said tubes connected to the grids thereof, phase shifting means linking said individual input circuits, said phase shifting means comprising a transmission line having an effective length equal to one-quarter the wave length of said input signal, a common input circuit connected to one end of said phase shifting means whereby an input signal may be applied to the grids of the same tube in opposite polarity and to corresponding grids of the different tubes with predetermined different relative phase, a second transmission line connected to the end of said first-named transmission line remote from said common input circuit, an electron discharge device coupled to the free end of said second-named transmission line, means for controlling the electron flow in said device in accordance with a modulating signal, thereby to vary said relative phase in accordance with said modulating signal, and a common output circuitconnected to said anodes, said output circuit comprising a transmission line having an effective length equal to one-quarter the wave length of said output signal.

6. A frequency multiplier modulator comprising a signal input circuit, two pairs of vacuum tube signal repeating means, each having a control grid and being adapted to repeat portions of a signal impressed thereon, two separate input circuits individually connected to said control electrodes for applying a signal to the control electrodes of each of said pairs of repeating means, phase-shifting means having a first pair of terminals and a second pair of terminals and capable of producing a phase shift between said first and said second pairs of terminals, means for connecting said signal input circuit and one of said separate input circuits to said first pair of terminals to apply to the control grids of the first pair of repeating means a signal in opposite polarity, means for connecting the second separate input circuit to said second pair of terminals to apply a signal to said grids of the second pair of signal repeating means, said signal being in opposite polarity with a predetermined different relative phase with respect .to the signals applied to said grids of said first pair of signal repeating means, an impedance means coupled to said second pair of terminals and variable in accordance with a modulating signal, thereby to vary the relative phase of said signal applied to said control grids, and an output circuit connected to said repeating means for combining signal portions repeated by said repeating means to produce a modulated signal of increased frequency.

'7. A frequency multiplier modulator comprising a pair of vacuum tubes. each having two grids and one anode, an input circuit, an impedance means having a iirst pair of terminals and a secondpair of terminals. said impedance means being capable of producing a phase shift between said rst and said second pairs of terminals, means connecting said input circuit and said grids of the rst of said vacuum tubes to said irst pair of terminals toapply to said grids a signal in opposite polarity, means connecting said grids of .the second of said vacuum tubes to said second pair of terminals to apply to said grids said signal in opposite polarity with a predetermined diilerent relative phase with respect to the signals applied to said grids of said first tube, means connected to said second pair of terminals for varying said relative phase in accordance with a modulating signal, and a common output circuit connected to said anodes to produce a modulated signal of increased frequency.

8. A frequency multiplier modulator comprising a signal input circuit, first vacuum tube signal repeating means comprising control electrode means for repeating half-cycles of a predetermined polarity only of a signal, second vacuum tube signal repeating means comprising control electrode means for repeating half-cycles of the opposite polarity only of said signal, a, plurality of separate input circuits individually connected to said first and second control electrode means, phase shifting means connecting said separate inputcircuits to said multiplier signal input circuit for applying said signal to said ilrst and secondl repeating means with predetermined dif-v ferent relative phase, means for varying said relative phase in accordance with a modulating signal and an output circuit connected to said repeating means for combining signal half-cycles repeated by sa-id first and second-repeating means to produce a modulated signal of increased frequency.

ARTHUR L. NELSON. 

